In electromagnetism, there are two kinds of dipoles:
An electric dipole deals with the separation of the positive and negative charges found in any electromagnetic system. A simple example of this system is a pair of electric charges of equal magnitude but opposite sign separated by some typically small distance. (A permanent electric dipole is called an electret.)
A magnetic dipole is the closed circulation of an electric current system. A simple example is a single loop of wire with constant current through it. A bar magnet is an example of a magnet with a permanent magnetic dipole moment.Dipoles, whether electric or magnetic, can be characterized by their dipole moment, a vector quantity. For the simple electric dipole, the electric dipole moment points from the negative charge towards the positive charge, and has a magnitude equal to the strength of each charge times the separation between the charges. (To be precise: for the definition of the dipole moment, one should always consider the "dipole limit", where, for example, the distance of the generating charges should converge to 0 while simultaneously, the charge strength should diverge to infinity in such a way that the product remains a positive constant.)
For the magnetic (dipole) current loop, the magnetic dipole moment points through the loop (according to the right hand grip rule), with a magnitude equal to the current in the loop times the area of the loop.
Similar to magnetic current loops, the electron particle and some other fundamental particles have magnetic dipole moments, as an electron generates a magnetic field identical to that generated by a very small current loop. However, an electron's magnetic dipole moment is not due to a current loop, but to an intrinsic property of the electron. The electron may also have an electric dipole moment though such has yet to be observed (see electron electric dipole moment).
A permanent magnet, such as a bar magnet, owes its magnetism to the intrinsic magnetic dipole moment of the electron. The two ends of a bar magnet are referred to as poles—not to be confused with monopoles, see Classification below)—and may be labeled "north" and "south". In terms of the Earth's magnetic field, they are respectively "north-seeking" and "south-seeking" poles: if the magnet were freely suspended in the Earth's magnetic field, the north-seeking pole would point towards the north and the south-seeking pole would point towards the south. The dipole moment of the bar magnet points from its magnetic south to its magnetic north pole. In a magnetic compass, the north pole of a bar magnet points north. However, that means that Earth's geomagnetic north pole is the south pole (south-seeking pole) of its dipole moment and vice versa.
The only known mechanisms for the creation of magnetic dipoles are by current loops or quantum-mechanical spin since the existence of magnetic monopoles has never been experimentally demonstrated.
The term comes from the Greek δίς (dis), "twice" and πόλος (polos), "axis".
Potential at the center of an electric dipole is zero. This doesn't make intuitive sense, how can work required to bring an arbitrary charge from infinity to the center of a dipole be zero? Imagine a charge at some distance on horizontal bisector of the dipole, it will deflect from the...
I need to take the derivative of the magnetic field from a magnetic dipole with respect to r for a project I'm working on:
B =[m[/0]/(4π) * (3rhat(μ dot rhat) - μ)/|r|^3
where rhat is the unit vector of the vector r (or r/|r|), |r| is the magnitude of the vector r, and μ is the magnetic...
Homework Statement
Consider a polarised sphere of radius R the polarization is given by
P vector = (ar^2 + b) r hat = ( ar+ b/r) r vector
Where a and b are constantHomework Equations
Find the dipole moment of the sphere
The Attempt at a Solution
I knew that P (polarized)= delta p / delta...
Homework Statement
consider s dipole with spacing of 2cm between the two sources. it is radiating a 100hz pure tone, and the magnitude of each source 'A' is given by 1n/M^2.
calculate the pressure as a function of the angle between the reciever and the dipole for a reciever 10 m from the dipole...
Ok we know for a Dipole the direction of Electric Field for points on the the dipole axis is in the direction of Dipole Moment(from -ve to +ve charge) rite? Now we also know that fields emanate from +ve charge and extend towards -ve charge. So what will be the direction of Electric Field at the...
I am stuck with considering a problem. I don't even really know where to start so any pointers would be a great help.
I am considering a semi-analytic model for some data i have. The situation is looking at how light propogates from a point source in diamond to air. At the surface of the...
Homework Statement
Consider the following species in the gaseous state: NF_3, \ BeF_2, \ BCl_3, \ KrF_4 \ and \ SeO^{2-}_4 .
Which of them have electric dipole moment?
Homework Equations
The Attempt at a Solution
I tried google, but I can't figure out how to check that..
Hi there.
If I wanted to calculate the radiation vector (in z > 0) produced by a short dipole with uniform current Io (+z direction) on a infinite perfect electric conductor (plane z=0), I'd have to apply the images method. So I'd have to calculate the radiation vector produced by two short...
Greetings,
I wonder with respect to what coordinates the formulas given for the electric dipole is valid. Also I want to comprehend the difference between pure and physical dipoles and why many books put the origin of the cartesian system they define on the middle point of the electric dipole...
QFT Question: What is meant by "dipole form"?
Hello physics people! Probably a very basic question, but here goes.
I'm taking a course on QFT based on Ryder. I've heard my professor refer to propagators as having a "polar" or "dipole" form. Things like (k^2 - m^2 + ie)^(-1)
For anyone who...
Homework Statement
Given a Electric dipole located at the origin of the coordinate system, which oscillates with a given frequency and amplitude, creating an electromagnetic wave. It is found that no power can be detected at point P1 = (3 y) m (i.e. the intensity of the wave at that point is...
Two permanent magnets are on the table some distance apart and having some arbitrary orientation relative to each other. When we let go of them they will rotate and translate until they stick together. I am looking for suitable equations to model this interaction on a computer. Also, if anyone...
Homework Statement
Cosnider two dipoles, p1 oriented along z at the origin, and p2 oriented along x at a distance r in the
x - y plane. Given that the torque on a dipole in a field E can be written N = p x E, find the torque on each dipole about its centre.
Homework Equations
N=pxE , E=...
Homework Statement
A point dipole p is at the origin of coordinates, while a point charge q is at position r. Calculate the potential energy U of this system in two ways (a) by treating the dipole as a source and q as a test charge in the dipole field (b) by treating the dipole as a...
Homework Statement
A spherical sheet of radius a has surface-charge density which depends on the polar angle θ according to the formula
σ(θ)=σ0+σ1cos(θ)
Find the total dipole moment
Homework Equations
pz=∫(dQ)z
z=rcosθ
The Attempt at a Solution
I calculated the 1st dipole...
According to Wikipedia, the source of all knowledge, the LHC contains some 1,232 dipole magnets with an additional 392 quadrupole magnets. What is the difference in function between the two types of magnets?
How might the effects of magnetic field gradients contribute to the differences...
Homework Statement
The HCl (hydrochloric acid) molecule has a dipole moment of about 3.4x10-30 C.m. The two atoms are separated by about 1.10-10 m. What is the net charge on each atom? What is maximal torque that this dipole will experience in a 5.104 N/C electric field? How much energy one...
Hi,
In quantum optics, when we talk about atom field interaction with a classical field and quantized atom, we say that the Hamiltonian has an interaction part of the form \hat{d}.\vec{E} where d is the dipole operator.
For a two level atom, the dipole operator has only off diagonal elements...
Homework Statement
NOTE: Coordinates are in centimeters.
A dipole consists of two point charges: +q = 0.911 μC at (-2.53,0) and -q at (2.53,0).
a) Calculate V, the potential created by the dipole at (31.9,82).
Homework Equations
V = k \frac{q}{r} \\
\\ r_{1} = \sqrt{(x-.0253)^2 +...
Hi
The energy U of a magnetic dipole in an external magnetic field is given by
U = -\mu \cdot B
so the energy is zero when they are perpendicular and maximal when they are antiparallel. This makes very good sense intuitively. Quantum-mechanically we have that
\mu = -m_Fg_F \mu_B...
Homework Statement
A Hertzian dipole at origin generates a signal in empty space which is detected at a wire loop with position vector;
r=(50m)ez
Homework Equations
Signal is detected by changing magnetic field;
B(t)=B0 sin(2∏ft)ex
Show it is consistent with the Maxwell's solution to a plane...
Homework Statement
I have a hertzian dipole at the origin, generating a signal. Nearby in empty space there is a loop, at a position vector r=(50m)ezz which can detect this signal.
Homework Equations
I have the equation B(t) = B0 sin (2*pi*ft)ex which I understand is the signal emitted...
Hi
In my book (Griffith's) there are two different expressions for the induced polarization, namely
P = \frac{N}{\text{volume}}<d>
where <d> is the average of the dipole operator and N the number of atoms. The other expression listed is
P = \text{Re}[\varepsilon_0 \chi E]
where E...
Homework Statement
Write code to calculate the input impedance on a thin wire antenna using the below form of Pocklington's integral equation. Use Method of moments.
Use a pulse as the basis function, point matching and delta-gap generator as the 'source'.
Assume the wire is broken up into 7...
In the below figure, I'm supposed to express the z-coordinate of the point P, z', by the angle \theta
Does this work out as z' = R\cdot \cos \theta? If so, I can't see why...
Please give me a hint on this.
Homework Statement
I have a long EM question in which there is a Hertzian dipole at a point (0,0,-100), (unknown orientation) and I am told the equation of the physical magnetic field detected 100m away at the origin of Cartesian coordinates. $$(B_0 \sin (2 \pi f t)\mathbf{e}_x$$, and $$B_0 =...
I have been trying to figure out which formula for the relationship between oscillator strength and transition dipole moment is correct.
Wiki had the following formula:
http://photonicswiki.org/index.php?title=Transition_Dipole_Moment
f = 4.703 \times 10^{29} \bar{v} \mu^{2}_{ge}\,\...
I have seen two formulas for a short dipole radiation resistance - according to one it is about 200*(l^2/λ^2) Ω, according to the second about 800*(l^2/λ^2) Ω.
Which of these is correct, if any? (Let us consider a resonant short dipole, connected to proper inductance).
In particular, I would...
Hi friends.
I am so new with Comsol software to design something but I wonder, if it is possible to desing a bending magnet (dipole) and simulate the motions of electrons ? I really would like to do this. Please give me a hand,help me to handle and try to do one together.
Best.
There are three compounds:
1.) fulvene
2.) calicene
3.) I don't know the name of the third compound. It looks like calicene except that there is not a double bond inside of the three-membered ring.
Anyways, it turns out that fulvene and calicene have unusually large dipole moments...
Hello, I have some questions about Dipole Moment, taken from a General Chemistry textbook, in which they treat Dipole Moment as a scalar. Here is a worked example from this textbook:
Homework Statement
The dipole moment of HCl is 1.11 D, and the distance between atoms is 127 pm. What is...
This is not a homework question I encountered this while revisiting the Electric Dipoles .
First of all if someone explains me why the dipole
So in the image above which way should the dipole rotate ? Anti Clock Wise or Clock Wise .
What My intuition says is the Energy of a dipole is
U...
Sometimes I am asked to compute the total dipole moment of a charge configuration. Normally you work with dipole moment per unit volume, so you can find the above by integrating over the entire volume, which is quite easy. I'm curius though, what is the physical interpretation of the total...
Hi,
I'm trying to find the input impedance of an OCF dipole and I need a sanity check by one of the more experienced guys here. Now, I have assumed that the voltage and current distribution along the line is always the same, no matter where you feed the antenna at [1]. The radiation resistance...
Homework Statement
4 charges are placed each at a distance 'a' from origin. The dipole moment of the configuration is:
a)2qa\hat{j}
b)3qa\hat{j}
c)2qa[\hat{i}+\hat{j}]
d)none
Homework Equations
The Attempt at a Solution
How do i determine dipole moment here when there is...
Reading a book about atomic transitions i really don't understand physically what the book means when it talks about differences between the population lifetime and the dipole lifetime that appear in the coerence part of the density matrix of a 2 or a 3 level system.
I imagine that the...
I am trying to understand the elctric dipole approximation when an atom interacts with an electromagnetic wave.
I know that if the size of the atom is much much smaller than the wavelength of the radiation, then the dot product od the wavevector and the position vector becomes constant.
I...
Hi friends as all know that the direction of electric dipole moment vector is from negative charge towards the positive charge. I am pretty confuse that this direction is allotted to the dipole moment vector with some reason or just by convention.
Homework Statement
Show that the energy of an ideal dipole in an electric field E is given by:
U = -p \bullet E
Homework Equations
The energy required to bring to charges together, their electrostatic energy, is:
W = ½ ƩqiV(ri)
The Attempt at a Solution
Well I want to know what the...
I'm confused about what polarization of a dielectric does to its electrical properties. It is clear to me that polarization causes every little atom to get a tiny dipole moment. A measure of the polarization is therefore P = dipole moment per unit volume. However, what is really a dipole moment...
Homework Statement
The electric potential of a grounded conducting sphere of radius r in a
uniform electric field E_{0}\hat{k}along the z direction is given by
V(r,\theta )=-E_{0}r\cos \theta +\frac{E_{0}R^{3}\cos \theta }{r^{2}}
where r is the distance from the centre of the sphere...
What is the physical meaning of electri dipole moment? What does it tell us about the dipole?
Please don't just throw away mathematical equation (p=qd r_hat); help me to get its physical sense!
Please help me with the attached question.
I don't understand how you get from the first line to the second line in (2). (I'm not too familiar with working with cross products and vectors).
Also, I don't know how you get (5) from (1) and (2).
Any help would be much appreciated. Thanks! :)
Homework Statement
Determine the dipole moment for the following charge distributions: 1.5uC each at (0,3), (0,5), where the coordinates are in cm.
Homework Equations
p=qd
The Attempt at a Solution
Since the coordinates are (0,3) and (0,5) d is 2cm or 0.02m and q is 1.5uC or...
Homework Statement
Determine the effective area (Aeff) for a short dipole with L = λ/60 and λ/2 dipole. If the wires used for dipoles has radii a = 1 cm compare Aeff with the physical area.
G(short dipole) = 1.5
G(half wave dipole) = 1.64
Homework Equations
Aeff = G* λ2/4*pi
The...
Homework Statement
How do I show that our equations for the E- and B-fields for the oscillating electric dipole do NOT satisfy Maxwell’s equations?
Homework Equations
After approximations in retarded potentials, we have our E- and B-field as following:
E =...
How do I show that our equations for the E- and B-fields for the oscillating electric dipole do NOT satisfy Maxwell’s equations?
After approximations in retarded potentials, we have our E- and B-field as following:
E = -ω2μ_{0}p_{0}(4∏r)-1sin(θ)cos[ω(t-\frac{r}{c})]\hat{θ} (Griffiths...
Homework Statement
A soft iron ball is fixed a distance d above the pole of a rectangular dipole magnet which is permanently magnetized. What is the force the iron ball feels due to the magnetic field?
The dimensions of the dipole magnet are a x a x b, where a < b
Homework Equations...